Document: draft-ietf-lsr-ospf-ls-link-infinity
Title: Advertising Unreachable Links in OSPF
Reviewer: Ladislav Lhotka
Review result: Ready with Issues
**** General comments
I have two questions regarding the overall logic of router functional
capabilities:
1. The ietf-ospf-unreachable-links module defines the "functional-capability"
identity that appears to be intended as a potential base for identities other
than "unreachable-link" that may be defined elsewhere. If it is the case, it
would be better to define the base identity "functional-capability" in a
special module.
2. Support for interpreting LSLinkInfinity as unreachable seems to be a feature
of a particular router implementation. Would it make sense to define a YANG
feature for it?
**** Specific comments
- The augment statement for "unreachable-link-advertisement" contains the
following substatement:
when "../rt:type = 'ospf:ospfv2' or "../rt:type = 'ospf:ospfv3'"
XPath equality check uses *literal strings*, so the above condition will fail
if another prefix is used for the "ietf-ospf" module in XML representation of
instance data, and will always fail for JSON representation where the
identityref values are "ietf-ospf:ospfv2" and "ietf-ospf:ospfv3".
This problem was the reason for defining XPath functions derived-from() and
derived-from-or-self(), see sec. 10.4 in RFC 7950.
- The remaining four augments use "when" statements like this:
when "derived-from(/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/rt:type, 'ospf:ospfv2')"
This avoids the above problem but won't work either because identity derivation
is irreflexive (see sec. 7.18.2 in RFC 7950), so the above expression will be
false if "rt:type" is "ospf:ospfv2". In all four cases the XPath function
derived-from-or-self() has to be used rather than derived-from().
**** Nits
- Section 3.1 uses "this document" and "this specification" but, as I
understand it, it means some prior OSPF spec and *not*
draft-ietf-lsr-ospf-ls-link-infinity. I would recommend to clarify this and
refer to a specific document explicitly.
- Typos:
* sec. 1, 2nd paragraph: s/his/This/
* sec. 3.1, 2nd paragraph: s/interpretaion/interpretation/
* sec. 3.1, 3rd paragraph: s/metic/metric/
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